import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class _7findSubstring {
    //串联所有单词的子串
    public List<Integer> findSubstring(String s, String[] words) {
        List<Integer> ret = new ArrayList<>();
        Map<String,Integer> hash1 = new HashMap<>();
        for(String str: words){
            hash1.put(str,hash1.getOrDefault(str,0)+1);
        }
        int len = words[0].length(), m = words.length;

        for(int i = 0; i < len;i++){
            Map<String,Integer> hash2 = new HashMap<>();

            for(int left = i,right = i,count = 0;right <= s.length()-len; right+=len){
                String in = s.substring(right,right+len);
                hash2.put(in,hash2.getOrDefault(in,0)+1);
                if(hash2.get(in) <= hash1.getOrDefault(in,0)) count++;
                while(right-left+1 > len*m){
                    String out = s.substring(left,left+len);
                    if(hash2.get(out) <= hash1.getOrDefault(out,0)) count--;
                    hash2.put(out,hash2.get(out)-1);
                    left+=len;
                }
                if(count == m) ret.add(left);
            }
        }
        return ret;
    }
}
